Issues Magazine

Models of Life: A Brief History

By By Alan Dorin

Associate Professor, Faculty of Information Technology, Monash University

As has been the case since clay was cutting-edge technology, making representations of life helps us to orient ourselves in an otherwise bewildering universe.

What is life? This question, in its many forms, has perplexed history’s greatest thinkers, and continues to do so despite its apparent simplicity.

A current view is that life describes collections of molecules that are self-organising and self-maintaining. Life acquires energy and materials from the environment, using them to arrange and build its own parts, and to keep itself together in the face of the natural tendency for it to come apart. The waste material from this activity is excreted. As well as the tendency to disintegrate, life opposes external forces that actively attempt to split it, crush it, dissolve it or just generally prevent it from maintaining itself. Some life uses energy for (loco)motion to acquire yet more resources or to evade being used as the fuel for another organism’s life. Life continues in a single body just long enough to reproduce so that its blueprint is represented in another generation.

In the English language the terms life and death are also applied metaphorically to the activities and failures of our machines and devices: the engine sprang to life; the battery died. But the distinction we make now between biology and technology has not always been important, or even recognised. And the self-organising properties we now use to tell life from non-life are relatively recent preferences that weren’t shared by many of our predecessors.

In the past it was likely that body-plan, self-movement, growth and reproduction were the traits used to distinguish life from non-life. For millennia, engineers and artists have attempted to recreate these aspects of living things using available technology. They are certainly still relevant characteristics, but the contemporary view of organisms as self-constructing machines offers a new and powerful approach to explaining life’s properties. An organism’s form and behaviour are said to “emerge” from the interactions of smaller cells, and these emerge in turn from the interactions of smaller molecules, and these from smaller atoms.

The chain of emergence also extends upwards in scale. From groups of organisms emerge communities and ecosystems, and, some have argued, all Earth’s ecosystems participate in a global form of life, Gaia, with its own emergent properties (e.g. climate).

So, what is the field of study or the activity known as Artificial Life? In its strongest sense, Artificial Life is the creation and study of technological organisms – the creation of real life using technology instead of biological reproduction. In a weaker sense, it is the mimicry of organisms for art or amusement, or it is the study of organisms through the proxy of technological models and representations.

Models are very powerful tools, especially in science. They allow us to test hypotheses, explore ramifications and demonstrate principles.

In science, therefore, it often doesn’t matter whether or not something technological is “truly” alive. It does, however, have the potential to matter for philosophical, ethical, moral, social or cultural reasons. But whether or not a particular piece of technology is really alive, or just a model, depends on your preferred definition of life.

Consequently, the boundary between strong and weak artificial life is mutable. Many historical examples of artificial life illustrate the relationship between our understanding of biology and human technological development.

Dust to Dust, Ashes to Ashes

Clay and earth are often cited as the material of choice for human-building in many people’s creation myths. This includes narratives from Africa, Asia, and the Judeo-Christian stories originating in ancient Mesopotamia. Hence it is not surprising that our ancestors from these regions would have attempted to recreate life using the same technology. Arguably the earliest relevant artefacts are the Venus figurines of Tan-Tan (200,000–500,000 BP, Morocco) and of Berekhat-Ram (230,000 BP, Golan Heights). These two objects are very crude approximations of the human body. Their basic shape is probably natural but they appear to have been enhanced with simple scraping and, in one case at least, pigment.

Another application of prehistoric technology to the recreation of life’s appearance is found in the cave paintings at Chauvet and Lascaux in France. These examples date to around 30,000 and 15,000 years ago, respectively. Some cave paintings by indigenous Australians are older still.

Sculpture and two-dimensional image-making have seen continuous development for millennia. They remain culturally significant media for modelling humans and other life visually.

Articulated Dolls

Between 1550 and ~1070 BCE, a toy cat with an articulated, string-operated jaw, and a small clay mouse with wagging tail and chattering mouth, were fashioned in Egypt. A little later, other animal miniatures were being placed on carts, or having axle-mounted wheels inserted through their legs to allow them to be moved smoothly. In the latter half of the first millennium BCE, terracotta dolls articulated at the hips and shoulders were produced in Corinth, Greece. Of course, articulated dolls and wheeled creatures are now a staple of toyshops worldwide. Puppets also existed in ancient Greece and have been in continuous production for at least a couple of thousand years. With these, the illusion of independent movement is maintained.

Completely self-moving puppets, or automata, were also manufactured in ancient Greece. Unfortunately the details of their operation remain sketchy. Their power source was possibly a twisted sinew or cord that seems to have been released by a trigger.

Pneumatics

Detailed documentation remains for many of the works of the ancient Greek, Hero of Alexandria, who lived in the first century CE. He followed a series of inventors who worked during the latter centuries BCE. These pioneers utilised the flow of water, pressurised air and escaping steam to power various devices, including self-moving figures of animals and humans engaged in simple activities such as making offerings to the gods, indicating the time, whistling (birds) and slurping water from a bowl (beasts).

Even Archimedes of Syracuse appears to have dabbled in this area; he designed a clock that allowed the time to be read by the changing colour of a Gorgon’s eyes!

Most interestingly, Hero designed a programmable cart that mimicked forward, reverse and turning motions typical of scurrying insects. The cart was powered by a falling lead weight drawing cords wound on axles. The weight’s fall was checked by grain draining through a small orifice, like sand within an hourglass. The technique was also used to power an automatic theatre with dancing Bacchantes (female followers) making offerings to the god Dionysus and accompanied by automatically played music.

Mechanical figures such as these remain popular tourist attractions today, especially in the town squares of Europe, where they are most often regulated by clockwork.

Clockwork

From around the 10th century CE in the Islamic Empire and in China, improvements were made to the water-driven techniques for controlling automata that were pioneered in ancient Greece. But some time towards the end of the 13th century a major technological advance arrived in Europe: verge escapement. An escapement is a part of a mechanical clock that uses the simple harmonic oscillations of a weighted beam, a pendulum or coiled balance spring to check and release the fall of a weight or unwind a spring.

This unshackled clocks and automata from the continuous flow of water or grain through an orifice. Clockwork now ushered in a host of new attempts at modelling and understanding biology by replicating even extremely complex motions of animals. To start with, mechanical “Jacks” were added to civic and personal clocks. These human figures, often holding strikers or hammers, rang the bells.

Over several centuries clockmakers and inventors devised automata of ever-increasing complexity. There were angels and devils; an extremely complex duck that ate, swallowed, waggled and defecated; and androids (human-shaped automata) that played real musical instruments, wrote poetry, delivered cups of tea, drew pictures or, in one case, drew an arrow from a quiver, strung a bow with it and shot at a distant target. For a time, clockwork automata were seemingly everywhere.

Towards the middle of the 17th century, the French philosopher René Descartes famously suggested that all animals, humans among them, were complex clockwork automata. Humans were distinguished from animals only by the presence of an immortal soul.

One hundred years later another French philosopher, Julien Offray de La Mettrie, proposed in his text, L’Homme Machine (first translated as Man, a Machine), that organisms were a kind of perpetual motion machine. In his view there was no need for souls to explain life’s behaviour, even in the case of humans.

But late in the 18th century a new discovery set people thinking along a different track.

Electricity

The Italian philosopher and physician Luigi Galvani discovered that electricity could be made to cause a frog’s legs to jump, even when the legs were no longer attached to the frog! Gruesome and mostly unsuccessful attempts were made after this to reanimate corpses salvaged from the gallows. This activity, and the high-society chatter that accompanied the issues it raised, partly inspired Mary Shelley to pen her famous Frankenstein; or, The Modern Prometheus (1818). From this story a host of movies, books and plays were born in which a mad scientist creates life from inanimate matter by wiring up flesh to lightning conductors and electrical contraptions.

Outside of fiction, electrically powered robots appeared in the 20th century, especially after World War II. The “tortoises” of Grey-Walter, a British roboticist, are particularly interesting. In their various incarnations these wheeled and shelled robots could be conditioned like Pavlov’s dogs to respond to a tap on their shell or an audible whistle. They could return to their hutches when their batteries ran down and could turn in response to the presence of a light source. Industrial robots – powerful, fast and accurate hydraulically actuated arms – began to replace some forms of human labour as the 20th century progressed. Japanese industry in particular became prominent and innovative in its use of robot technology for manufacturing.

As this was happening, a revolution in information technology that had begun in the late 1940s was also shaping the way representations of life were being constructed.

Software

In the middle of the 20th century, Hungarian-American mathematician (among other things) John von Neumann, British mathematician and computer scientist (among other things) Alan Turing and Italian-Norwegian mathematician Nils Aall Barricelli laid the groundwork for relating general-purpose computing machinery to biology. In particular, von Neumann investigated the creation of self-reproducing machines, Turing explored the mathematics of complex chemical pattern formation (such as that responsible for the development of organisms from single cells) and Barricelli experimented with evolutionary processes realised in computer software.

The discipline of Artificial Life as it is practised now owes much to these three men, and to pioneers in robotics such as Grey-Walter. There is still very much research being conducted in all of these areas.

One of my personal research interests involves using computer code to understand the impact of human activities on ecosystems. Some focus has shifted towards the synthesis of self-organising and self-maintaining machines, as indicated earlier.

But even without this recent interest in emergence, software that mimics or recreates biological self-replication, evolution and pattern formation, and hardware that matches biological life in its diversity and complexity of behaviour, continues to offer new insights into the phenomenon of life.

The examples described here and many others are explored in the author’s free multiplatform eBook, Biological Bits (http://www.csse.monash.edu.au/~aland/BiologicalBits.html).